Two-component magnets have come into use in motors in response to requirements for the maximum possible magnetic flux on the one hand, and coercive field intensity in order to prevent demagnetization phenomena, on the other. It is not possible to satisfy both these requirements with a single magnetic material, because magnetic materials having high remanence have low coercive field intensity, and magnetic materials with a high coercive field intensity have low remanence. The danger of demagnetization of a magnet used in a motor is particularly great at the ends of the magnet, and is especially apparent when starting the motor at low temperatures and at the trailing edge. It has been proposed to use two-component magnets with highly coercive magnetic material at the trailing edge, and otherwise fabricating the magnet of a magnetic material having the greatest possible remanence. The material of maximum remanence has, however, lesser coercive field intensity in comparison with the highly coercive material.
The sections of the different materials are adjacent to one another in the circumferential direction of the motor; these sections of different magnetic material extend in the axial direction of the armature and protrude beyond the armature at either end by some distance. This axial magnetic overhang results in a further substantial increase in flux, i.e. 26%, given a magnet length 1.4 times the armature length, for example, and with a ratio of the armature diameter to the armature length of 1.83.